Powder actuated tool

ABSTRACT

A captive piston type of powder actuated tool is provided with a barrel pivotally engaged by the forward end of the tool housing so that the breech end of the barrel can be upraised into a loading position. A piston retractor is slidably carried on the barrel and includes a member extending through a slot in the barrel for engaging the head of the piston used for moving of a piston into a firing position. The barrel may be pivotally returned to firing position only after the piston retractor has been moved forwardly and out of the way of piston movement in the subsequent firing of the tool.

United States Patent [72] Inventor Raymond V. Pomeroy 3,029,435 4/1962Kopfet al. 227/10 Portland, Oreg. 3,172,119 3/1965 Siddons 227/8 2 l No,737,900 3,172,120 3/1965 DeCaro et al. 227/10 [22] Filed June 18, 19683,297,224 1/1967 Osborne 227/10 [45] Patented Feb. 16, 1971 3,348,75110/1967 Henmng 227/8 Asslgnee Omark Industries Primary ExaminerGranvilleY. Custer, Jr.

g g Oregon AttorneyBuckhorn, Blore, Klarquist & Sparkman acorpo a n EDTOL [54] POWDER ACTUA-T ABSTRACT: A captive piston type of powderactuated tool is 23 Claims, Drawing Figs.

provided with a barrel pivotally engaged by the forward end of [52] U.S.Cl 227/8, the tool h i so that the breech end of the barrel can be227/10 upraised into a loading position. A piston retractor is slidably[51] Int. Cl B25c 1/14 carried on the barrel and includes a memberextending [50] Field ofSearch 227/8, 9, l0 through a slot in the barrelfor engaging the head of the piston used for moving of a piston into afiring position. The barrel [56] References Cited may be pivotallyreturned to firing position only after the UNITED STATES PATENTS pistonretractor has been moved forwardly and out of the way 3,022,513 2/1962Temple et al. 227/8 ofpiston movement in the subsequent firing of thetool.

2 T76 26 I4 24 25 3 3a [6 42 46 13 l5 ll "1 21 59 5317 gir i &L 4% 4'"Y*'i i-- I00 9596 2 4 I02 92 I as so 62' raises-L439 PATENT ED FEB 161971 SHEET 2 OF 2 RAYMOND V. POM EROY INVENTOR BUCKHORN, BLORE,KLARQUIST & SPARKMAN ATTORNEYS BACKGROUND OF THE INVENTION Piston typeexplosively actuated tools, e.g. for driving fastener devices intoconcrete or masonry walls, conventionally employ a blank cartridge forproviding the explosive gases applied to drive the fastener device. Sucha tool is cocked by pressure of the muzzle against a workpiece or wall,resulting in movement of the tools breechblock into a firing position. Acartridge may then be fired to force the captive piston through thebarrel and drive the fastener device. After firing, the barrel and thebreechblock are conventionally separated so that a new cartridge orpower load may be inserted, and the captive piston must be returned toits firing position. Various constructions have been employed heretofore to facilitate the loading and piston return operations. The barrelmay be rotated laterally to the side of the tool facilitating theremoval of the captive piston to a firing position and insertion of anew load. Alternatively, the barrel may be movable longitudinallyforward of the tool for retraction of the piston and reloading. In thecase of these constructions and other similar arrangements, the toolmechanism is apt to be quite complex and/or somewhat unbalanced.

SUMMARY OF THE INVENTION According to the present invention a powderactuated tool comprises a housing including a rearward breech portionand a forward barrel portion. The tool's barrel is cradled by the barrelportion when the barrel is in a first position in substantial alignmentwith the tool's breechblock. The barrel is pivotally engaged by thebarrel portion at a forward location so that the breech end of thebarrel can be pivotally upraised away from the breechblock into aloading position. The tool further includes a piston retractor slidablycarried by the barrel, which retractor includes a member for engagingthe piston, and a handle portion which is manually engageable for movingthe piston retractor. The piston may be moved thereby to a firingposition toward the breech end of the barrel. The retractor and housingconstruction prevent the barrel from being pivotable back into firingposition in alignment with the breechblock until such retractor is movedforwardly out of the way of the captive piston, allowing firing of thetool. The tool is compact, and movement of component parts thereof isreduced to a minimum.

It is accordingly an object of the present invention to provide animproved powder actuated tool of the captive piston type which is betterbalanced, more compact, and more easily manufactured.

It is a further object of the present invention to provide an improvedpowder actuated tool of the captive piston type wherein movement ofcomponent parts of the tool relative to the housing thereofis minimized.

It is another object of the present invention to provide an improvedpowder actuated tool of the captive piston type which is quiet inoperation.

It is another object of the presentinvention to provide an improvedpowder actuated tool of the captive piston type which is easy tooperate.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. The invention, however, both as to organization andmethod of operation, together with further advantages and objectsthereof, may best be understood by reference to the followingdescription taken in connection with the accompanying drawings whereinlike reference characters refer to like element.

DRAWINGS FIG. I is a longitudinal cross section of a powder actuatedtool according to the present invention;

FIG. 2 is a lateral cross section of the FIG. I tool taken at 2-2 inFIG. I;

FIG. 3 is a lateral view of the cross section of the FIG. It tool takenat 3-3 in FIG. 1;

FIG. 4 is a top view partially broken away in horizontal cross sectionof the FIG. 1 tool; and

FIG. 5 is a side view of the FIG. 1 tool in a loading position thereof.

DETAILED DESCRIPTION Referring to the drawings, an explosively operatedtool includes a housing generally indicated at 10 including a forwardportion 12 which may be designated as a barrel portion and a rearwardportion 13 which may be designated as a breech portion. Rearward portion13 includes a handle portion or grip 118. Barrel portion 12 issemicircular in cross section and cradles barrel 14 in a first positionthereof wherein the barrel is aligned with the breechblock 16 positionedin the breech portion of the housing. Barrel M extends from muzzle 15rearwardly to a power plug 118 received in the breech end of the barrel.The barrel is provided with an inner bore 20 within which a captivepiston 22 is slidable, such piston having an enlarged piston head 24which slides within inner bore 20 and a ram or plunger 26 adapted tocontact and drive the head of a fastener device (not shown) into aworkpiece at the left end of muzzle l5. Enlarged head 24 of the captivepiston includes a rearward head portion 25 and a forward head portion 27slidably engaged with the inside of the barrel bore. Head portion 25 issuitably provided with a piston ring or seal 32 therearound to preventexcessive escape of gas past head 24.

Power plug 18 is slidably positioned in the breech end of barrel bore 20wherein the bore 20 is substantially smooth. The outer circumference ofpower plug 18 is grooved and provided with a spring retainer 34 whichreleasably secures the power plug at the end of the barrel. Power plug18 includes a chamber 36 for the receiving a power charge or cartridge.

Breechblock 16 is longitudinally slidable within breech portion 13 ofthe housing and is recessed at 38 to receive power plug 18 in the firingpositionthereof. Breechblock 16 slidably carries firing pin holder 40 inturn carrying a tapered firing pin 42. The firing pin holder is normallyheld in a retracted position relative to breechblock 16 by sear 44 whichis urged at this time by spring 46 to a location adjacent an edge 48 ofthe breechblock. When the tool is cocked and the breechblock is forcedto the right into a cocked position against the spring bias of springs50 and 52, sear 44 will be aligned with trigger bar 54 and can be movedupwardly by trigger bar 54. When breechblock I6 is in such cockedposition, firing pin spring 56 is compressed, and upward movement of thesear 44 causes tapered firing pin 42 to be driven by spring 56 intotapered bore 58 in the breechblock 16. The firing pin 42 is adapted toproject through tapered bore 58 and strike a rim fire power load or thelike positioned in chamber 36. To fire the tool, trigger 60 iscompressed against spring 62 moving trigger bar 54 upward into contactwith sear 44, providing the latter is in cocked position. Trigger bar 54is carried in a vertical slot in the trigger and is pivoted at 57, beingmaintained in alignment with the trigger by internal spring 59. Thismechanism permits the trigger bar 54 to turn in a clockwise mannerwithout damage in the event that the tool is cocked with the triggercompressed. In this event, trigger bar 54 will merely rotate in aclockwise sense as the side of sear 44 contacts the same. The tool maythen not be fired until the trigger is released and compressed again.

The barrel portion 12 of the housing, being semicircular in crosssection, is substantially channel-shaped and open upwardly where itreceives or cradles cylindrical barrel 14 in the first position of thebarrel in alignment with breechblock 16. The barrel 14 is pivotallyengaged by the barrel portion 12 of the housing at a location towardsthe muzzle end of the barrel so that the breech end of the barrel can beupraised away from the breechblock into loading position. Asubstantially horizontal pin member 64 is carried by the barrel portionof the housing at the aforementioned location toward the muzzle end ofthe barrel, pin member 64 being positioned at the lower side of thebarrel and extending transversely of the tool. A pinmatchinglongitudinal and transverse slot 66 is located on the underside ofbarrel 14 through which pin member 64 extends. Slot 66 has longitudinallength along the barrel permitting longitudinal sliding movement of thebarrel for full engagement of power plug 18 within recess 38 ofbreechblock 16, as well as movement of the breechblock 16 within breechportion 13 of the housing into the aforementioned cocked position. Thus,in FIG. 1, dimension X substantially corresponds at least to the depthof penetration of power plug 18 within recess 38, and dimension Ycorresponds to the movement of breechblock 16 further to the right tothe cocked position wherein sear 44 is above trigger bar 54. Thus,barrel 14, when moved to the left by the distance X, will clear powerplug 18 from breechblock l6, and when moved to the right by the distanceY, will compress breechblock 16 against the bias of springs 50 and 52until sear 44 is over trigger bar 54.

The barrel portion 12 is provided with an arched barrel retaining member68 proximate and above the location of pin member 64. The arched barrelretaining member 68 has an inner surface 70 semicircular in crosssection which substantially matches the cylindrical barrel 14, but whichis angled upwardly and to the right in FIG. 1. It will be apparent thatbarrel 14 may be moved to the left by a distance X whereby power plug 18clears breechblock l6, and then the breech end of the barrel may bemoved upwardly into a loading position, with the barrel pivotingsubstantially around pin member 64. At this time, arched barredretaining member 68 limits the upward movement of the barrel, and whenbarrel 14 is upraised as far as it will go, the inner surface 70 of theretaining member substantially matches or cradles the upper side ofbarrel 14. Retaining member 68 prevents the barrel from moving away frompin member 64 by a distance as great as the diameter of pin member 64 sothat the barrel pivots substantially around pin member 64.

The barrel 14 is provided with a longitudinal slot 72 on the undersidethereof or the side adjacent barrel portion 12 of the housing. Thislongitudinal slot does not extend the full length of the barrel, butstops short of the breech and muzzle ends thereof as illustrated. Thus,ring 32 on piston head 24 is located a predetermined distance towardpower plug 18 from the breech end of slot 72 in the firing position ofthe piston. Also, the muzzle end of slot 72 is proximate an insert orstop 74 located at the left end or muzzle end of barrel 14.

The tool is provided with a piston retractor 76 carried by the barrel.This piston retractor comprises a ring slidably mounted on the exteriorof the cylindrical barrel and fitted on the outside of the barrel foreasy slidable movement therealong. The retractor 76 is provided with apair of horizontal handles 78 and 80 extending horizontally outwardlyfrom the retractor and just above the upper edges of barrel portion 12of the housing toward the muzzle end thereof adjacent retaining member68. Retractor 76 includes a member 82 for engaging piston head portion27 as when the piston 22 has moved toward the muzzle end of the barrel.As illustrated in H0. 5, barrel 14 may be upraised by pivoting aroundpin member 64, after which either of the handles 78 or 80 may then begrasped to move retractor 76 to the right. Member 82 engages headportion 27 as retractor 76 is moved to the right, bringing with itpiston 22 until the piston is returned to the right end or breech end ofbarrel 14. Then, retractor 76 is moved to the left-hand positionillustrated in the drawings, and indeed must be before barrel 14 can bereturned to a position in alignment with breechblock 16. The barrelportion 12 of the housing is cut down at 90 to receive handles 78 and 80only when retractor 76 is in its forwardmost position. Moreover, thebarrel portion of the housing includes wedge-shaped recess 92 forreceiving a lower wedge-shaped portion 94 of the retractor only when theretractor is returned to its left-hand position. Therefore, theretractor 76 is removed out of the way of the movement of piston 22 whenthe tool is in firing position, thereby avoiding danger to the operatorof the tool from undesired movement of retractor 76 when the tool isfired.

Lower wedge-shaped portion 94 of retractor 76 carries member 82 in avertical slot 96 at the middle thereof, with the L-shaped member 82being pivotally secured in the slot at its rearward end by means ofhorizontal pin 98. A setscrew 100 in wedge-shaped portion 94 of theretractor normally maintains member 82 in its operating position shown.However, for disassembly of the tool, the retractor 76 is movedrearwardly toward the breech end of the upraised barrel (as illustratedin H6. 5) and the setscrew 100 may be loosened whereby member 82 can bepivoted out of engagement with slot 72 in the barrel. This allows theretractor 76 to be slid off the barrel.

Piston 22 is provided with an ejector 86 which may protrude into chamber36 for ejecting power load or cartridge 88. The ejector 86 is tapered atits rearwardmost end where it may extend into chamber 36. This taperedconfiguration acts to guide explosion gases along the chamber withminimum lateral deflection of such gases during firing of the tool toprevent chamber erosion. This construction is more fully described inthe copending application of Yung Shing Hsu entitled, Chamber ErosionPreventing Powder Actuated Tool," Ser. No. 675,140, filed Oct. 13, 1967,and assigned to the assignee of the present invention.

In barrel portion 12 of the housing underneath barrel 14 and betweenrecess 92 and breechblock 16 there is located a muffier recess 102extending longitudinally of the barrel portion of the housing. Thismufi'ler recess 102 is closed at the top by liner 104, forming a part ofthe barrel portion of the housing, and secured by screw 106, except forlongitudinal slot 108 substantially matching slot 72 in the barrel.Muffler recess 102 is desirably provided with an internal muffier 110here comprising a loosely coiled roll of sheet metal. The axis of theroll of sheet metal is disposed in recess 102 in a directionlongitudinal of the tool, and the outer end of the roll of sheet metalis oriented upwardly toward slot 108, so the outer entrance of thepassage between convolutions of the roll opens toward such slot toreceive the explosion gases. The explosion gases tend to take a pathbetween convolutions of the roll, this circuitous path tending todissipate the energy thereof.

As the tool is fired, a power load explodes and combustion explosiongases enter bore 20 of barrel 14 forcing piston 22 to the left. As headportion 25 moves past the breech end of slot 72, these gases are ventedalong slot 72 and leave around retractor 76. However, to diminish thereport of the tool when fired, these gases also expand into recess 102and through the muffier convolutions..Such gases enter and eventuallyleave recess 102 through slot 108.

The captive piston 22 is tapered between head 24 and ram or plunger 26,and this tapered portion and head 24 have a low hardness and highductility as compared with a high hardness and little or no ductility ofstop 74. The hard metal stop 74 includes a long cylindrical entrancebore 114 and a frustoconical die portion 116. The bore 114 serves toslidably receive the muzzle end of the piston head 24, to the left ofhead portion 25, should the captive piston 22 be overdriven so that ram26 extends outwardly at the left of muzzle 15. Should the piston thus beoverdriven, piston energy is dissipated by extruding, by frustoconicaldie portion 116, the tapered portion of the captive piston 22. Theconstruction allows the dissipation of energy of an overdriven pistonwithout damage to the captive piston inasmuch as bore 114 laterallysupports the captive piston during overdriving so as to prevent bendingof the head portion of the piston. This energy-dissipating mechanism isfurther described and claimed in the copending application of Yung ShingHsu and Raymond V. Pomeroy, Ser. No. 796,980, filed Feb. 6, 1969.

In the general operation of the tool according to the present invention,a fastener device is inserted in muzzle l5 and the user grasps a handleportion or grip 118 and forces the fastener device against a workpiecesuch as a masonry wall or the like. Urging the tool against a workpiecebrings about full contact between power plug 18 and breechblock l6, and

further urges the breechblock rearwardly of the tool into a I cockedposition, i.e. placing sear 4M above trigger bar 54. The trigger 60 maynow be compressed raising sear 44 such that firing pin $2 is driven tothe left exploding a cartridge or power load in chamber 36. Explosivegases enter the inner bore of barrel M behind the head 24 of the captivepiston driving the captive piston to the left and forcing the fastenerdevice into the workpiece. As hereinbefore mentioned, explosive gasesleave through slot 72 as the head portion 25 passes the breech end ofslot 72 from what may be considered a combustion chamber inside thebarrel to the right of slot 72 in FIG. I. These gases leave directlythrough the length of slot 72, but muffler recess 102 provides anexpansion chamber for these gases which pass through muffler 1H0 wherebythe noise of the explosion is reduced. The muffler breaks up the gas tomuffle the sound.

To reload the tool, and return the captive piston to firing position,the barrel is moved to the left in F IG. l by a distance, X, and thebreech end thereof is pivoted upwardly around horizontal pin member 64.In practice, the tool may be grasped by means of grip 1113 and snappedin a downward direction causing the barrel M to lower and pivot aroundhorizontal pin member 64 so that the breech end of the barrel includingpower plug 16 tilts away from the breechblock. With the barrel in theout-tilted position, a handle 78 or 80 of the retractor 76 is graspedand pulled rearwardly. As a result, member 82 engages the outer edge ofhead portion 27 pulling the piston 22 to the right, back to a firingposition. The movement of the piston, as head portion 25 reaches thebreech end of slot 72, may force shell or power load 88 from chamber 36.if ejection is not accomplished by air pressure, the ejector contactsthe cartridge for forcibly removing the same. The retractor is thenreturned to its forwardmost position by means of handles 78 or 80, and anew cartridge or power load is inserted in chamber 36. The barrel 14 isthen pivoted back into alignment with breechblock 16 for the nextoperation. It is thus seen that the operation of the tool according tothe present invention is simple and construction thereof is compact. Thetool retains a compact and balanced construction, and, since the weightof the tool is well balanced, the tool is easy to handle.

It should be noted that when the tool is urged against a workpiece,retractor 76 is automatically urged to the rear of wedge-shaped recess92, assuming the retractor is not already in such position. With thetool forced against a workpiece, the retractor 76 is held in positionbetween the breech end of recess 92 and the muzzle end ofslot 72. Themuzzle end ofslot 72 engages the inwardly extending portion of member82. Therefore, when the tool is fired, no undesired movement ofretractor 76 will take place. It should be noted that even if the piston22 should be overdriven into stop 74, the edge of head portion 27 willnot strike or move member 82 with the retractor 76 in its lockedposition between the edges of recess 92 and slot 72.

While I have shown and described a preferred embodiment of my invention,it will be apparent to those skilled in the art that many changes andmodifications may be made without departing from my invention in itsbroader aspects. I therefore intend the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

lclaim:

ii. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a firstposition in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading position;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end of said barrel; and

a piston retractor slidably carried by said barrel, said retractorincluding a member extending into said barrel for engaging said pistonand a handle portion which is manually engageable for moving said pistonretractor and said piston to a firing position toward the breech end ofsaid barrel.

2. The tool according to claim 1 wherein said barrel is provided with alongitudinal slot ending short of the breech and muzzle ends of saidbarrel, and wherein said member for engaging said piston extends throughsaid longitudinal slot in said barrel for engaging the head of saidpiston at the muzzle end thereof.

3. The tool according to claim 2 wherein the head of the piston isprovided with an ejector extending from the breech end of the head.

4. The tool according to claim 2 wherein said barrel portion of thehousing is channel-shaped and open upwardly, said slot in said barrelbeing located on the lower side of said barrel toward said barrelportion of the housing.

5. The tool according to claim 1 including a power plug received in thebreech end of said barrel for receiving a power load cartridge, with thebreechblock being movable rearwardly within said breech portion of saidhousing from an uncocked to a fully cocked or triggerable position, andwherein the barrel, in addition to being pivotally engaged by the barrelportion of said housing, is also slidable with respect to the barrelportion of said housing into full engagement with said breechblock andis further rearwardly slidable for urging said breechblock into a cockedposition in response to pressure of the muzzle end of the barrel againsta workpiece.

6. The tool according to claim 5 wherein said captive piston includes ahead provided with an ejector extending from the breech end of said headfor ejecting a cartridge from the power plug when said piston retractormoves the captive piston to the firing position.

7. The tool according to claim 5 including a substantially horizontalpin member carried by said barrel portion of said housing at saidlocation toward the muzzle end of said barrel, said pin member beingpositioned at the lower side of said barrel, and a matching slot in theunderside of said barrel through which said pin member extends, saidlast mentioned slot having a longitudinal length along said barrelpermitting longitudinal sliding movement of the barrel for fullengagement with the breechblock plus movement of the breechblock into acocked position.

8. The tool according to claim 1 wherein the barrel portion of thehousing is substantially semicircular in cross section for cradling acylindrical barrel, and is provided with an arched barrel-retainingmember proximate said location toward the muzzle end of the barrel forsubstantially enclosing the upper side of the barrel at such location,said arched barrel-retaining member having an inner semicircular surfacefor substantially matching the cylindrical barrel in an upraisedposition thereof and for limiting the upward movement of the barrel.

9. The tool according to claim 8 including a substantially horizontalpin member carried by said barrel portion of said housing at saidlocation toward the muzzle end of the barrel, and at the lower side ofsaid barrel, and a matching slot in the underside of said barrel throughwhich said pin member extends, said last mentioned slot having alongitudinal length along said barrel for permitting longitudinalslidable movement of the barrel for full engagement with the breechblockplus movement of the breechblock into a cocked position.

10. A powder actuated tool comprising:

a housing including a rearward breech portion and a for ward barrelportion;

a breechblock carried by said breech portion;

a barrel cradled. by said barrel portion when said barrel is in a firstposition in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading position;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end ofsaid barrel;

and a piston retractor ring slidably carried on said barrel, said ringcarrying a member for engaging the head of said captive piston byengaging the head of said piston on the muzzle end thereof;

handle means extending outwardly from either side of said ring formoving said ring and said piston to a firing position toward the breechend of said barrel; and

said barrel being provided with a longitudinal slot ending short of thebreech and muzzle ends of said barrel, wherein said member for engagingthe head of said captive piston extends through said longitudinal slotin said barrel.

1]. The tool according to claim 1 wherein said barrel portion of saidhousing matingly receives said piston retractor allowing location ofsaid barrel in said first position only when said piston retractor islocated far enough toward the muzzle end of said barrel so that saidmember for engaging the captive piston does not interfere with themovement of the captive piston in driving said fastener element.

12. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a firstangular position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading position;

said barrel also being slidable with respect to the barrel portionofsaid housing in and out ofcocked position;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end ofsaid barrel;

a piston retractor slidably carried by said barrel, said retractorincluding a member for engaging said piston for moving said piston to afiring position toward the breech end ofsaid barrel; and

said barrel portion of said housing including a recess for receiving aportion of said piston retractor toward the muzzle end of the barrelportion of the housing when said barrel is in said first angularposition, the piston retractor being restrained between a portion ofsaid barrel and said recess in the barrel portion of said housing whensaid barrel is in its cocked position so that said piston retractor willnot be struck by movement of said piston in response to explosion of thepower load.

13. The tool according to claim 2 including a power plug received in thebreech end of said barrel for holding a power load, said breechblockbeing movable within said breech portion of said housing from anuncocked to a fully cocked or triggerable position, wherein the barrel,in addition to being pivotally engaged by the barrel portion of saidhousing, is also rearwardly slidable with respect to the barrel portionof said housing into full engagement with said breechblock and isfurther rearwardly slidable for urging said breechblock into a cockedposition in response to pressure of the muzzle end of the barrel againsta workpiece, and wherein said barrel portion of said housing includes arecess for receiving said piston retractor toward the muzzle end of thebarrel portion of the housing when said barrel is in said firstposition, the piston retractor being restrained between the muzzle endof the slot in the barrel and the rearward end of the recess in thebarrel portion of the housing when the barrel is in a cocked position.

14. The tool according to claim 1 including a power plug received in thebreech end of said barrel for receiving a power load, said barrel havinga substantially smooth inner bore at the breech end thereof, with saidpower plug being slidably received therewithin and yieldably retainedwithin said inner bore.

15. The tool according to claim 14 wherein said power plug includes acircumferential groove, and spring retaining means mounted within saidgroove for bearing against the inner bore ofsaid barrel.

16. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a firstposition in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading position;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end ofsaid barrel;

a piston retractor slidably carried by said barrel, said retractorincluding a member for engaging said piston and a handle portion whichis manually engageable for moving said piston retractor and said pistonto a firing position toward the breech end of said barrel; and

said tool further including a slot in said barrel at least adjacent thebreech end of said barrel, said barrel portion of said housing includinga muffler recess communicating with said slot in said barrel when saidbarrel is in said first position.

17. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a firstposition in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading posi tion;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end of said barrel;

a piston retractor slidably carried by said barrel, said retractorincluding a member for engaging said piston and a handle portion whichis manually engageable for moving said piston retractor and said pistonto a firing position toward the breech end of said barrel;

said barrel being provided with a longitudinal slot ending short of thebreech and muzzle ends of said barrel, and wherein said member forengaging said piston extends through said longitudinal slot in saidbarrel for engaging the head of said piston at the muzzle end thereof;and

said barrel portion of said housing including a muffler recesscommunicating with said longitudinal slot in said barrel when saidbarrel is in said first position, wherein explosive gases from saidbarrel travel through said slot and into said recess as the head of saidcaptive piston moves past the breech end of said longitudinal slot, saidgases further passing along said longitudinal slot toward the muule endofsaid barrel, and a muffler in said muffler recess.

18. A powder actuated tool comprising:

a housing including a rearward breech "portion and a forward barrelportion;

a breechblock carried by said breech portion and movable within saidbreech portion of said housing from an uncocked to a fully cocked ortriggerable position;

said breechblock also carrying a triggerable firing pin;

trigger means for operating said firing pin when said breechblock is ina cocked position;

a barrel cradled by said barrel portion of said housing, when saidbarrel is in a first position in substantial alignment with saidbreechblock;

a substantially horizontal pin member carried by said barrel portion ofsaid housing at a location toward the muzzle end of said barrel, saidhorizontal pin member being positioned at the lower side of said barrel;

a power plug positioned at the breech end of said barrel having achamber communicating with said barrel for receiving a power loadadapted to be fired by said firing pin;

a matching first slot in the underside of said barrel through which saidhorizontal pin member extends, said first slot having a longitudinallength along such barrel permitting longitudinal sliding movement of thebarrel for full engagement of the power plug with the breechblock plusmovement of the breechblock into a cocked position as the barrel isurged toward a workpiece;

said barrel being pivotable about horizontal pin member so that thebreech end of said barrel including said power plug can be upraised awayfrom said breechblock into a loading position when the barrel carryingthe power plug is withdrawn from engagement with said breechblock;

said barrel portion of said housing being provided with an arched barrelretaining member proximate and above the location of said horizontal pinmember for substantially enclosing the upper side of the barrelproximate said location, said arched barrel retaining member having aninner surface semicircular in cross section for substantially matchingthe upper side of the barrel in an upraised position of the barrel forlimiting the upward movement of the barrel;

said barrel having a longitudinal second slot on the underside of thebarrel ending short of the breech and muzzle ends of said barrel;

a captive piston longitudinally slidable within said barrel and movablein response to an explosion of the power load in the power plug fordriving a fastener element;

a ring-shaped piston retractor slidably carried on the exterior of saidbarrel, said retractor including a member for engaging said pistonthrough a longitudinal second slot in the barrel and a handle portionwhich is manually engageable for moving said piston retractor and saidpiston to a firing position toward the breech end of said barrel; and

said barrel portion of said housing including a recess for receivingsaid piston retractor toward the muzzle end of the barrel portion whenthe barrel is in a position of alignment with the breechblock such thatsaid piston retractor does not interfere with the movement of saidcaptive piston in response to explosion of the power load.

19. The tool according to claim 1 further including means for preventingmovement of said barrel into said first position until said pistonretractor is positioned far enough toward the muzzle end of said barrelso that said member for engaging said piston does not interfere with themovement of said piston in driving said fastener element.

20. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel carried by said barrel portion and provided with a longitudinalslot ending short of the breech and muzzle ends of said barrel andthrough which explosive gases may escape from said barrel;

a captive piston longitudinally slidable within said barrel and movablein res onse to explosion of a power load for driving a fastener e ementmto a workpiece at the muzzle end of said barrel;

said barrel portion of said housing being provided with a muffler recesscommunicating with said slot near the breech end thereof for receivingexpansion of explosive gases from said barrel as the head of the captivepiston passes the breech end of said longitudinal slot; and

a muffler in said muffler recess, wherein said muffler comprises a rollof sheet metal located in said muffler recess.

21. A powder actuated tool comprising:

a housing including 'a rearward breech portion and a forward barrelportion;

a breechblock carried by said breech portion;

a barrel carried by said barrel portion and provided with a longitudinal"slot ending short of the breech and muzzle ends of said barrel andthrough which explosive gases may escape from said barrel;

a captive piston longitudinally slidable within said barrel and movablein response to explosion of a power load for driving a fastener elementinto a workpiece at the muzzle end of said barrel;

said barrel portion of said housing being provided with a muffler recesscommunicating with said slot near the breech end thereof for receivingexpansion of explosive gases from said barrel as the head of the captivepiston passes the breech end of said longitudinal slot;

a muffler in said recess; and

wherein said barrel portion of said housing includes a longitudinal slotmatching the breech end portion of said longitudinal slot in saidbarrel, said muffler recess being closed except for the longitudinalslot in the barrel portion of the housing communicating therewith.

22. The tool according to claim 21 wherein said muffler comprises aloosely coiled roll of sheet metal disposed in said recess with the axisof the roll in a direction longitudinal of said tool.

23. The tool according to claim 22 wherein an outer end of said roll isoriented upwardly so the outer entrance of the passage between theconvolutions of the roll opens toward said first mentioned longitudinalslot.

1. A powder actuated tool comprising: a housing including a rearwardbreech portion and a forward barrel portion; a breechblock carried bysaid breech portion; a barrel cradled by said barrel portion when saidbarrel is in a first position in substantial alignment with saidbreechblock; said barrel being pivotally engaged by the barrel portionof said housing at a location toward the muzzle end of said barrel sothat the breech end of said barrel can be upraised away from saidbreechblock into a loading position; a captive piston longitudinallyslidable within said barrel and movable in response to explosion of apower load for driving a fastener element into a workpiece at the muzzleend of said barrel; and a piston retractor slidably carried by saidbarrel, said retractor including a member extending into said barrel forengaging said piston and a handle portion which is manually engageablefor moving said piston retractor and said piston to a firing positiontoward the breech end of said barrel.
 2. The tool according to claim 1wherein said barrel is provided with a longitudinal slot ending short ofthe breech and muzzle ends of said barrel, and wherein said member forengaging said piston extends through said longitudinal slot in saidbarrel for engaging the head of said piston at the muzzle end thereof.3. The tool according to claim 2 wherein the head of the piston isprovided with an ejector extending from the breech end of the head. 4.The tool according to claim 2 wherein said barrel portion of the housingis channel-shaped and open upwardly, said slot in said barrel beinglocated on the lower side of said barrel toward said barrel portion ofthe housing.
 5. The tool according to claim 1 including a power plugreceived in the breech end of said barrel for receiving a power loadcartridge, with the breechblock being movable rearwardly within saidbreech portion of said housing from an uncocked to a fully cocked ortriggerable position, and wherein the barrel, in addition to beingpivotally engaged by the barrel portion of said housing, is alsoslidable with respect to the barrel portion of said housing into fullengagement with said breechblock and is further rearwardly slidable forurging said breechblock into a cocked position in response to pressureof the muzzle end of the barrel against a workpiece.
 6. The toolaccording to claim 5 wherein said captive piston includes a headprovided with an ejector extending from the breech end of said head forejectiNg a cartridge from the power plug when said piston retractormoves the captive piston to the firing position.
 7. The tool accordingto claim 5 including a substantially horizontal pin member carried bysaid barrel portion of said housing at said location toward the muzzleend of said barrel, said pin member being positioned at the lower sideof said barrel, and a matching slot in the underside of said barrelthrough which said pin member extends, said last mentioned slot having alongitudinal length along said barrel permitting longitudinal slidingmovement of the barrel for full engagement with the breechblock plusmovement of the breechblock into a cocked position.
 8. The toolaccording to claim 1 wherein the barrel portion of the housing issubstantially semicircular in cross section for cradling a cylindricalbarrel, and is provided with an arched barrel-retaining member proximatesaid location toward the muzzle end of the barrel for substantiallyenclosing the upper side of the barrel at such location, said archedbarrel-retaining member having an inner semicircular surface forsubstantially matching the cylindrical barrel in an upraised positionthereof and for limiting the upward movement of the barrel.
 9. The toolaccording to claim 8 including a substantially horizontal pin membercarried by said barrel portion of said housing at said location towardthe muzzle end of the barrel, and at the lower side of said barrel, anda matching slot in the underside of said barrel through which said pinmember extends, said last mentioned slot having a longitudinal lengthalong said barrel for permitting longitudinal slidable movement of thebarrel for full engagement with the breechblock plus movement of thebreechblock into a cocked position.
 10. A powder actuated toolcomprising: a housing including a rearward breech portion and a forwardbarrel portion; a breechblock carried by said breech portion; a barrelcradled by said barrel portion when said barrel is in a first positionin substantial alignment with said breechblock; said barrel beingpivotally engaged by the barrel portion of said housing at a locationtoward the muzzle end of said barrel so that the breech end of saidbarrel can be upraised away from said breechblock into a loadingposition; a captive piston longitudinally slidable within said barreland movable in response to explosion of a power load for driving afastener element into a workpiece at the muzzle end of said barrel; anda piston retractor ring slidably carried on said barrel, said ringcarrying a member for engaging the head of said captive piston byengaging the head of said piston on the muzzle end thereof; handle meansextending outwardly from either side of said ring for moving said ringand said piston to a firing position toward the breech end of saidbarrel; and said barrel being provided with a longitudinal slot endingshort of the breech and muzzle ends of said barrel, wherein said memberfor engaging the head of said captive piston extends through saidlongitudinal slot in said barrel.
 11. The tool according to claim 1wherein said barrel portion of said housing matingly receives saidpiston retractor allowing location of said barrel in said first positiononly when said piston retractor is located far enough toward the muzzleend of said barrel so that said member for engaging the captive pistondoes not interfere with the movement of the captive piston in drivingsaid fastener element.
 12. A powder actuated tool comprising: a housingincluding a rearward breech portion and a forward barrel portion; abreechblock carried by said breech portion; a barrel cradled by saidbarrel portion when said barrel is in a first angular position insubstantial alignment with said breechblock; said barrel being pivotallyengaged by the barrel portion of said housing at a location toward themuzzle end of said barrel so that the breech end of said barrel can beupRaised away from said breechblock into a loading position; said barrelalso being slidable with respect to the barrel portion of said housingin and out of cocked position; a captive piston longitudinally slidablewithin said barrel and movable in response to explosion of a power loadfor driving a fastener element into a workpiece at the muzzle end ofsaid barrel; a piston retractor slidably carried by said barrel, saidretractor including a member for engaging said piston for moving saidpiston to a firing position toward the breech end of said barrel; andsaid barrel portion of said housing including a recess for receiving aportion of said piston retractor toward the muzzle end of the barrelportion of the housing when said barrel is in said first angularposition, the piston retractor being restrained between a portion ofsaid barrel and said recess in the barrel portion of said housing whensaid barrel is in its cocked position so that said piston retractor willnot be struck by movement of said piston in response to explosion of thepower load.
 13. The tool according to claim 2 including a power plugreceived in the breech end of said barrel for holding a power load, saidbreechblock being movable within said breech portion of said housingfrom an uncocked to a fully cocked or triggerable position, wherein thebarrel, in addition to being pivotally engaged by the barrel portion ofsaid housing, is also rearwardly slidable with respect to the barrelportion of said housing into full engagement with said breechblock andis further rearwardly slidable for urging said breechblock into a cockedposition in response to pressure of the muzzle end of the barrel againsta workpiece, and wherein said barrel portion of said housing includes arecess for receiving said piston retractor toward the muzzle end of thebarrel portion of the housing when said barrel is in said firstposition, the piston retractor being restrained between the muzzle endof the slot in the barrel and the rearward end of the recess in thebarrel portion of the housing when the barrel is in a cocked position.14. The tool according to claim 1 including a power plug received in thebreech end of said barrel for receiving a power load, said barrel havinga substantially smooth inner bore at the breech end thereof, with saidpower plug being slidably received therewithin and yieldably retainedwithin said inner bore.
 15. The tool according to claim 14 wherein saidpower plug includes a circumferential groove, and spring retaining meansmounted within said groove for bearing against the inner bore of saidbarrel.
 16. A powder actuated tool comprising: a housing including arearward breech portion and a forward barrel portion; a breechblockcarried by said breech portion; a barrel cradled by said barrel portionwhen said barrel is in a first position in substantial alignment withsaid breechblock; said barrel being pivotally engaged by the barrelportion of said housing at a location toward the muzzle end of saidbarrel so that the breech end of said barrel can be upraised away fromsaid breechblock into a loading position; a captive pistonlongitudinally slidable within said barrel and movable in response toexplosion of a power load for driving a fastener element into aworkpiece at the muzzle end of said barrel; a piston retractor slidablycarried by said barrel, said retractor including a member for engagingsaid piston and a handle portion which is manually engageable for movingsaid piston retractor and said piston to a firing position toward thebreech end of said barrel; and said tool further including a slot insaid barrel at least adjacent the breech end of said barrel, said barrelportion of said housing including a muffler recess communicating withsaid slot in said barrel when said barrel is in said first position. 17.A powder actuated tool comprising: a housing including a rearward breechportion and a forwarD barrel portion; a breechblock carried by saidbreech portion; a barrel cradled by said barrel portion when said barrelis in a first position in substantial alignment with said breechblock;said barrel being pivotally engaged by the barrel portion of saidhousing at a location toward the muzzle end of said barrel so that thebreech end of said barrel can be upraised away from said breechblockinto a loading position; a captive piston longitudinally slidable withinsaid barrel and movable in response to explosion of a power load fordriving a fastener element into a workpiece at the muzzle end of saidbarrel; a piston retractor slidably carried by said barrel, saidretractor including a member for engaging said piston and a handleportion which is manually engageable for moving said piston retractorand said piston to a firing position toward the breech end of saidbarrel; said barrel being provided with a longitudinal slot ending shortof the breech and muzzle ends of said barrel, and wherein said memberfor engaging said piston extends through said longitudinal slot in saidbarrel for engaging the head of said piston at the muzzle end thereof;and said barrel portion of said housing including a muffler recesscommunicating with said longitudinal slot in said barrel when saidbarrel is in said first position, wherein explosive gases from saidbarrel travel through said slot and into said recess as the head of saidcaptive piston moves past the breech end of said longitudinal slot, saidgases further passing along said longitudinal slot toward the muzzle endof said barrel, and a muffler in said muffler recess.
 18. A powderactuated tool comprising: a housing including a rearward breech portionand a forward barrel portion; a breechblock carried by said breechportion and movable within said breech portion of said housing from anuncocked to a fully cocked or triggerable position; said breechblockalso carrying a triggerable firing pin; trigger means for operating saidfiring pin when said breechblock is in a cocked position; a barrelcradled by said barrel portion of said housing, when said barrel is in afirst position in substantial alignment with said breechblock; asubstantially horizontal pin member carried by said barrel portion ofsaid housing at a location toward the muzzle end of said barrel, saidhorizontal pin member being positioned at the lower side of said barrel;a power plug positioned at the breech end of said barrel having achamber communicating with said barrel for receiving a power loadadapted to be fired by said firing pin; a matching first slot in theunderside of said barrel through which said horizontal pin memberextends, said first slot having a longitudinal length along such barrelpermitting longitudinal sliding movement of the barrel for fullengagement of the power plug with the breechblock plus movement of thebreechblock into a cocked position as the barrel is urged toward aworkpiece; said barrel being pivotable about horizontal pin member sothat the breech end of said barrel including said power plug can beupraised away from said breechblock into a loading position when thebarrel carrying the power plug is withdrawn from engagement with saidbreechblock; said barrel portion of said housing being provided with anarched barrel retaining member proximate and above the location of saidhorizontal pin member for substantially enclosing the upper side of thebarrel proximate said location, said arched barrel retaining memberhaving an inner surface semicircular in cross section for substantiallymatching the upper side of the barrel in an upraised position of thebarrel for limiting the upward movement of the barrel; said barrelhaving a longitudinal second slot on the underside of the barrel endingshort of the breech and muzzle ends of said barrel; a captive pistonlongitudinally slidable within said barrel and movable in response to anexplOsion of the power load in the power plug for driving a fastenerelement; a ring-shaped piston retractor slidably carried on the exteriorof said barrel, said retractor including a member for engaging saidpiston through a longitudinal second slot in the barrel and a handleportion which is manually engageable for moving said piston retractorand said piston to a firing position toward the breech end of saidbarrel; and said barrel portion of said housing including a recess forreceiving said piston retractor toward the muzzle end of the barrelportion when the barrel is in a position of alignment with thebreechblock such that said piston retractor does not interfere with themovement of said captive piston in response to explosion of the powerload.
 19. The tool according to claim 1 further including means forpreventing movement of said barrel into said first position until saidpiston retractor is positioned far enough toward the muzzle end of saidbarrel so that said member for engaging said piston does not interferewith the movement of said piston in driving said fastener element.
 20. Apowder actuated tool comprising: a housing including a rearward breechportion and a forward barrel portion; a breechblock carried by saidbreech portion; a barrel carried by said barrel portion and providedwith a longitudinal slot ending short of the breech and muzzle ends ofsaid barrel and through which explosive gases may escape from saidbarrel; a captive piston longitudinally slidable within said barrel andmovable in response to explosion of a power load for driving a fastenerelement into a workpiece at the muzzle end of said barrel; said barrelportion of said housing being provided with a muffler recesscommunicating with said slot near the breech end thereof for receivingexpansion of explosive gases from said barrel as the head of the captivepiston passes the breech end of said longitudinal slot; and a muffler insaid muffler recess, wherein said muffler comprises a roll of sheetmetal located in said muffler recess.
 21. A powder actuated toolcomprising: a housing including a rearward breech portion and a forwardbarrel portion; a breechblock carried by said breech portion; a barrelcarried by said barrel portion and provided with a longitudinal slotending short of the breech and muzzle ends of said barrel and throughwhich explosive gases may escape from said barrel; a captive pistonlongitudinally slidable within said barrel and movable in response toexplosion of a power load for driving a fastener element into aworkpiece at the muzzle end of said barrel; said barrel portion of saidhousing being provided with a muffler recess communicating with saidslot near the breech end thereof for receiving expansion of explosivegases from said barrel as the head of the captive piston passes thebreech end of said longitudinal slot; a muffler in said recess; andwherein said barrel portion of said housing includes a longitudinal slotmatching the breech end portion of said longitudinal slot in saidbarrel, said muffler recess being closed except for the longitudinalslot in the barrel portion of the housing communicating therewith. 22.The tool according to claim 21 wherein said muffler comprises a looselycoiled roll of sheet metal disposed in said recess with the axis of theroll in a direction longitudinal of said tool.
 23. The tool according toclaim 22 wherein an outer end of said roll is oriented upwardly so theouter entrance of the passage between the convolutions of the roll openstoward said first mentioned longitudinal slot.